Clinicopathological significance of immune complex (IC) along the tubular basement membrane (TBM) in lupus nephritis

Abstract This paper reports on the clinicopathological significance of IC along the TBM in lupus nephritis. Renal biopsies were performed on 60 patients with SLE. All of the patients demonstrated immunoglobulin deposits in the glomeruli, and 16 of them also showed immune deposits along the TBM. The IgG in the glomeruli or along the TBM completely disappeared after incubation with human IgG, IgG Fc fragments, but not with human F(ab')2, rabbit or rat IgG. These results suggest that IgG along the TBM are similar in nature to IC in the glomeruli and that the IC are composed of IgG rheumatoid factor. The square of tubulointerstitial lesions was more severe in the group with IgG along the TBM than in the group with no IgG along the TBM (5.85 +/- 9.88% vs 1.29 +/- 3.72%). In addition of this, the group with IgG deposits along the TBM frequently demonstrated type IV lupus nephritis. Although the renal function was not significantly different in the both groups, the serum complement level was lower in the cases with IC deposits in the TBM. From these results, it is suggested that IC deposits along the TBM as one of the important inflammatory agents lead to the severe forms of tubulointerstitial injury and show the active stage of the disease in SLE patients.